Method for Manufacturing Electrode Comprising Polymeric Solid Electrolyte and Electrode Obtained Thereby

ABSTRACT

The present disclosure relates to an electrode for an all solid-state battery and a method for manufacturing the same. The electrode comprises an electrode active material layer, wherein the gaps between the electrode active material particles forming the electrode active material layer are filled with a mixture of a polymeric solid electrolyte and a conductive material. The method for manufacturing the electrode comprises a solvent annealing process, and the contact between the electrode active material particles and the conductive material is improved through the solvent annealing process, thereby improving ion conductivity of the electrode and capacity realization in the battery.

Cross-Reference to Related Applications

This application is a national phase entry under 35 U.S.C. § 371 ofInternational Application No. PCT/KR2019/005376 filed May 3, 2019, whichclaims priority from Korean Patent Application No. 10-2018-0051475 filedMay 3, 2018, all of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a method for manufacturing anelectrode comprising a polymeric solid electrolyte and an electrodeobtained thereby.

BACKGROUND ART

A lithium ion battery using a liquid electrolyte has a structure inwhich a negative electrode and positive electrode are defined by aseparator, and thus may cause a short-circuit when the separator isdamaged by deformation or external impact, resulting in a risk, such asoverheating or explosion. Therefore, it can be said that development ofa solid electrolyte capable of ensuring safety is a very importantproblem in the field of lithium ion secondary batteries.

A lithium secondary battery using a solid electrolyte has enhancedsafety, prevents leakage of an electrolyte to improve the reliability ofa battery, and facilitates manufacture of a thin battery. In addition,lithium metal may be used as a negative electrode to improve energydensity. Thus, such a lithium secondary battery using a solidelectrolyte has been expected to be applied to a high-capacity secondarybattery for electric vehicles in addition to a compact secondarybattery, and has been spotlighted as a next-generation battery.

However, a lithium secondary battery using a solid electrolyte has lowerion conductivity as compared to a battery using a liquid electrolyte andparticularly shows degradation of output characteristics at lowtemperature. In addition, such a solid electrolyte is problematic inthat it shows lower surface adhesion to an active material, as comparedto a liquid electrolyte, to cause an increase in interfacial resistance,and is distributed while not being in contact with an electrode activematerial to cause degradation of output characteristics or capacitycharacteristics as compared to the amount of a conductive materialintroduced to an electrode.

FIG. 1 is a schematic view illustrating an electrode for an allsolid-state battery comprising a polymeric solid electrolyte accordingto the related art. FIG. 1 shows an electrode 100 having an electrodeactive material layer 120 formed by coating slurry containing electrodeactive material particles 121, a conductive material 123 and a polymericsolid electrolyte 122 on a current collector 110, followed bycompression. Since the interfacial contact between the electrode activematerial particles and the polymeric solid electrolyte is poor, abattery obtained by using such an electrode shows limited realization ofcapacity. If severe compression is carried out in order to increase thecontact area between the active material particles and the polymericsolid electrolyte, the active material particles may be cracked. Forthese reasons, when using a polymeric solid electrolyte, it is notpossible to realize capacity sufficiently as compared to an electrodeusing a liquid electrolyte. Thus, the capacity is lower than thedesigned or theoretical capacity.

DISCLOSURE Technical Problem

The present disclosure is designed to solve the problems of the relatedart, and therefore the present disclosure is directed to providing anelectrode which has improved energy density by increasing the contactarea between electrode active material particles and a polymeric solidelectrolyte to improve lithium ion transportability and ion conductivityand to enhance capacity realized by the electrode and outputcharacteristics. The present disclosure is also directed to providing amethod for manufacturing the above-mentioned electrode.

Technical Solution

The present disclosure relates to an electrode for an all solid-statebattery and a method for manufacturing the same.

According to the first embodiment of the present disclosure, there isprovided an electrode for an all solid-state battery which comprises anelectrode active material layer comprising a plurality of electrodeactive material particles, a polymeric solid electrolyte and aconductive material, wherein the gaps between the electrode activematerial particles are filled with the polymeric solid electrolyte, thepolymeric solid electrolyte comprises a swellable polymer electrolyte,the polymeric solid electrolyte is in a swelled state by solventinfiltration, and the electrode active material layer has a porosity of0-18%.

According to the second embodiment of the present disclosure, there isprovided the electrode for an all solid-state battery as defined in thefirst embodiment, wherein the polymeric solid electrolyte undergoesvolumetric swelling by the infiltration of a vaporized organic solvent.

According to the third embodiment of the present disclosure, there isprovided the electrode for an all solid-state battery as defined in thefirst or the second embodiment, which is obtained through a solventannealing process, wherein the porosity of the electrode active materiallayer is reduced by the solvent annealing and the difference in porositybetween before and after the solvent annealing process is 0.5% or more.

According to the fourth embodiment of the present disclosure, there isprovided the electrode for an all solid-state battery as defined in anyone of the first to the third embodiments, wherein the porosity isreduced by the swelling of the polymeric solid electrolyte after thesolvent annealing process.

According to the fifth embodiment of the present disclosure, there isprovided the electrode for an all solid-state battery as defined in anyone of the first to the fourth embodiments, wherein the polymeric solidelectrolyte is a solid polymer electrolyte formed by adding a polymerresin to a solvated lithium salt.

According to the sixth embodiment of the present disclosure, there isprovided an all solid-state battery comprising the electrode as definedin any one of the first to the fifth embodiments. The all solid-statebattery comprises a positive electrode, a negative electrode and a solidelectrolyte layer interposed between the positive electrode and thenegative electrode, wherein at least one of the positive electrode orthe negative electrode is the electrode as defined in any one of thefirst to the fifth embodiments.

Meanwhile, there is also provided a method for manufacturing anelectrode for an all solid-state battery. According to the seventhembodiment of the present disclosure, there is provided a method formanufacturing an electrode for an all solid-state battery, comprisingthe steps of: preparing slurry for forming an electrode active materiallayer containing electrode active material particles, a polymeric solidelectrolyte and a conductive material; coating the slurry on at leastone surface of a current collector to obtain a preliminary electrode;and subjecting the preliminary electrode to a solvent annealing processto obtain an electrode.

According to the eighth embodiment of the present disclosure, there isprovided the method as defined in the seventh embodiment, wherein thepolymeric solid electrolyte is a solid polymer electrolyte formed byadding a polymer resin to a solvated lithium salt.

According to the ninth embodiment of the present disclosure, there isprovided the method as defined in the seventh or the eighth embodiment,wherein the solvent annealing process comprises the steps of:introducing the preliminary electrode to a sealed space; filling thesealed space with a vaporized solvent; and allowing the preliminaryelectrode to stand in the sealed space filled with the vaporizedsolvent.

According to the tenth embodiment of the present disclosure, there isprovided the method as defined in any one of the seventh to the ninthembodiments, wherein the solvent annealing process is carried out for1-72 hours.

According to the eleventh embodiment of the present disclosure, there isprovided the method as defined in any one of the ninth and the tenthembodiments, wherein the solvent is at least one of an aprotic solventselected from N,N-dimethylacetamide (DMAc), N-methyl pyrrolidone (NMP),dimethyl sulfoxide (DMSO) or N,N-dimethylformamide (DMF); or a proticsolvent selected from water, methanol, ethanol, propanol, n-butanol,isopropyl alcohol, decalin, acetic acid or glycerol.

According to the twelfth embodiment of the present disclosure, there isprovided the method as defined in any one of the seventh to the eleventhembodiments, wherein the polymeric solid electrolyte undergoesvolumetric swelling by the infiltration of the vaporized organicsolvent.

According to the thirteenth embodiment of the present disclosure, thereis provided the method as defined in any one of the seventh to thetwelfth embodiments, wherein the vaporized solvent has a temperature of15-200° C.

Advantageous Effects

In the electrode according to the present disclosure, the contact areabetween the electrode active material particles and the polymeric solidelectrolyte is increased to provide increased reaction sites of theelectrode active material. In addition, since the conductive material isdistributed in such a manner that it is positioned more closely to theperiphery of the active material particles, the contact frequencybetween the conductive material and the electrode active materialparticles is increased. As a result, it is possible to increase lithiumion transportability during charge/discharge, thereby improving capacityrealization of the electrode.

DESCRIPTION OF DRAWINGS

The accompanying drawings illustrate a preferred embodiment of thepresent disclosure and together with the foregoing disclosure, serve toprovide further understanding of the technical features of the presentdisclosure, and thus, the present disclosure is not construed as beinglimited to the drawing. Meanwhile, shapes, sizes, scales or proportionsof some constitutional elements in the drawings may be exaggerated forthe purpose of clearer description.

FIG. 1 is a schematic view illustrating an electrode comprisingelectrode active material particles, a polymeric solid electrolyte and aconductive material according to the related art.

FIG. 2 is a schematic view illustrating infiltration of solvent steam tothe electrode comprising electrode active material particles, apolymeric solid electrolyte and a conductive material according to anembodiment of the present disclosure.

FIG. 3 is a schematic view illustrating an electrode comprisingelectrode active material particles, a polymeric solid electrolyte and aconductive material according to an embodiment of the presentdisclosure.

BEST MODE

Hereinafter, preferred embodiments of the present disclosure will bedescribed in detail with reference to the accompanying drawings. Priorto the description, it should be understood that the terms used in thespecification and the appended claims should not be construed as limitedto general and dictionary meanings, but interpreted based on themeanings and concepts corresponding to technical aspects of the presentdisclosure on the basis of the principle that the inventor is allowed todefine terms appropriately for the best explanation. Therefore, thedescription proposed herein is just a preferable example for the purposeof illustrations only, not intended to limit the scope of thedisclosure, so it should be understood that other equivalents andmodifications could be made thereto without departing from the scope ofthe disclosure.

Throughout the specification, the expression ‘a part ┌comprises┘ anelement’ does not preclude the presence of any additional elements butmeans that the part may further include the other elements.

As used herein, the terms ‘approximately’, ‘substantially’, or the like,are used as meaning contiguous from or to the stated numerical value,when an acceptable preparation and material error unique to the statedmeaning is suggested, and are used for the purpose of preventing anunconscientious invader from unduly using the stated disclosureincluding an accurate or absolute numerical value provided to helpunderstanding of the present disclosure.

As used herein, the expression ‘A and/or B’ means ‘A, B or both ofthem’.

The present disclosure relates to a method for manufacturing anelectrode for a lithium ion secondary battery and an electrode obtainedthereby. According to the present disclosure, the lithium ion secondarybattery is an all solid-state battery using a polymeric solidelectrolyte. According to the present disclosure, the all solid-statebattery may also be referred to as a lithium polymer secondary batteryor lithium ion polymer secondary battery.

According to an embodiment of the present disclosure, the electrodecomprises an electrode active material layer comprising a plurality ofelectrode active material particles, a polymeric solid electrolyte and aconductive material, wherein the gaps between the electrode activematerial particles are filled with the polymeric solid electrolyte, andthe polymeric solid electrolyte is in a swelled state by solventinfiltration so that lithium ion transportability may be increased. Inaddition, according to an embodiment of the present disclosure, theconductive material is positioned in the gaps between the electrodeactive material particles so that electrical conductivity may beincreased. In other words, according to an embodiment of the presentdisclosure, the electrode active material particles in the electrodeactive material layer are integrated with one another through dot-to-dotand/or face-to-face binding mainly by means of the polymeric solidelectrolyte. In addition, the conductive material is dispersed in thepolymeric solid electrolyte. According to an embodiment of the presentdisclosure, the polymeric solid electrolyte may comprise a swellablepolymer electrolyte. For example, the polymeric solid electrolyte maycomprise a swellable polymer electrolyte in an amount of 50 vol % ormore, 70 vol % or more, 80 vol % or more, 90 vol % or more, or 95 vol %or more. Otherwise, the polymeric solid electrolyte may totally comprisea swellable polymer electrolyte. As used herein, the swellable polymerelectrolyte refers to one that comprises a polymer material andundergoes volumetric swelling by the infiltration of an organic solvent.Therefore, the polymeric solid electrolyte in the electrode according tothe present disclosure may be in an expanded (swelled) state at apredetermined ratio by solvent infiltration. Therefore, the gaps betweenactive material particles are filled with the swelled polymer (polymerelectrolyte), and thus the porosity of the electrode active materiallayer is decreased and the contact area between the polymer electrolyteand the active material particles is increased in the electrode activematerial layer, thereby providing effects of improving thecharacteristics of a battery, comprising effects of reducing resistanceand increasing capacity.

To accomplish such effects, it is preferred that the polymeric solidelectrolyte according to the present disclosure can be swelled bysolvent annealing. In addition, the polymeric solid electrolyte coversthe surface of electrode active material particles and/or fills the gapsbetween the electrode active material particles, and may be one having abroad electric potential window. For example, in the case of a positiveelectrode, the polymeric solid electrolyte may be one having highoxidation stability. In addition, in the case of a negative electrode,the polymeric solid electrolyte may be one having high reductionstability. For example, in terms of oxidation stability, the polymericsolid electrolyte may comprise a polycarbonate-based polymerelectrolyte, polysiloxane-based polymer electrolyte, phosphazene-basedpolymer electrolyte, or the like. In terms of reduction stability, thepolymeric solid electrolyte may comprise a polyether-based polymerelectrolyte.

According to an embodiment of the present disclosure, the polymericsolid electrolyte may be swelled at a ratio larger than 1% to 1,000%through the solvent annealing process. Within the above-defined range,the swelling ratio may be 50% or more, 100% or more, 200% or more, 300%or more, 400% or more, 500% or more, 600% or more, 700% or more, or 800%or more. When the polymeric solid electrolyte has a swelling degreelower than the above-defined range, it is not possible to improve theinterfacial contact between the active material and the electrolytesufficiently. When the polymeric solid electrolyte is swelled at a ratioexcessively higher than the above-defined ratio, the electrode has anexcessively large thickness to cause degradation of energy density. Theswelling degree of the polymeric solid electrolyte may be affected bythe molecular weight and/or crosslinking degree of the polymer material.The polymeric solid electrolyte is swelled more, when it has a smallermolecular weight and has a lower or no crosslinking degree.

In general, ‘swelling’ means a phenomenon in which a material absorbs asolvent and its volume is expanded. As used herein, ‘swelling degree’ isobtained by measuring the volume of a polymeric solid electrolyte before(the initial volume) and after solvent annealing and calculating avolumetric increment therefrom, and may be expressed by the followingFormula 1). For example, when a polymeric solid electrolyte has aswelling degree of 100%, it can be said that the electrolyte volume isdoubled as compared to the volume before solvent annealing. According tothe present disclosure, the solvent annealing means that a polymericsolid electrolyte is exposed to a vaporized organic solvent for apredetermined time so that the vaporized organic solvent may infiltrateinto the electrolyte. The exposure is carried out in a sealed spacesaturated with the steam of organic solvent, the exposure time may becontrolled to 1-72 hours, and the temperature may be controlled to15-200° C. According to an embodiment of the present disclosure, thetemperature may be 30° C. or more, 50° C. or more, 80° C. or more, 100°C. or more, 120° C. or more, or 150° C. or more, and 140° C. or less,130° C. or less, 120° C. or less, 100° C. or less, or 80° C. or less,within the above-defined range.

Swelling degree (%)={(Volume of polymeric solid electrolyte aftersolvent annealing−Initial volume of polymeric solid electrolyte)/Initialvolume of polymeric solid electrolyte}×100   Formula 1)

For example, the polymeric solid electrolyte may be one having theabove-defined range of swelling degree according to Formula 1), when itis exposed to saturated N-methyl pyrrolidone (NMP) steam atmosphere at atemperature of 30° C. for 24 hours. Otherwise, Formula 1) may also beused to set solvent annealing conditions (solvent, temperature and/orexposure time) capable of providing the above-defined range of swellingdegree to a selected polymeric solid electrolyte.

As described hereinafter, the electrode for an all solid-state batteryaccording to the present disclosure is obtained through a solventannealing process after manufacturing a preliminary electrode. Herein,the polymeric solid electrolyte is swelled by the infiltration ofvaporized solvent. Thus, the finished electrode has porosity lower thanthe porosity of the preliminary electrode. According to an embodiment ofthe present disclosure, the difference in porosity between the finishedelectrode for an all solid-state battery and the preliminary electrodemay be 0.5% or more, 1% or more, 5% or more, or 10% or more. Inaddition, the finished electrode for an all solid-state battery has alarger height as compared to the preliminary electrode.

According to an embodiment of the present disclosure, the polymericsolid electrolyte mainly functions to transport lithium ions in theelectrode and may be one having a desired ion conductivity, such as 10⁻⁷S/cm or 10⁻⁴ S/cm or more.

According to an embodiment of the present disclosure, one or morepolymeric solid electrolytes may be used suitably in order to supplementelectrode characteristics and to realize characteristics of electrodeactive material particles.

According to an embodiment of the present disclosure, the ionconductivity may be determined by measuring the electrochemicalimpedance of an electrolyte material by using a tester, such as VMP3(Bio logic science instrument) and applying the nyquist plot assessmentto the measured result. According to the present disclosure, thepolymeric solid electrolyte may be a polymer solid electrolyte formed byadding a polymer resin to a solvated lithium salt.

For example, the polymer solid electrolyte may comprise any one selectedfrom the group consisting of a polyether polymer, polycarbonate polymer,acrylate polymer, polysiloxane polymer, phosphazene polymer,polyethylene derivatives, alkylene oxide derivatives, phosphate polymer,polyagitation lysine, polyester sulfide, polyvinyl alcohol,polyvinylidene fluoride and polymer containing an ionically dissociablegroup, or a mixture of two or more of them. However, the scope of thepresent disclosure is not limited thereto.

According to an embodiment of the present disclosure, the polymer solidelectrolyte may comprise a polymer resin selected from the groupconsisting of a polymer resin, such as a branched copolymer comprisingpolyethylene oxide (PEO) backbone copolymerized with a comonomercomprising an amorphous polymer, such as PMMA, polycarbonate,polydiloxane (pdms) and/or phosphazene, comb-like polymer andcrosslinked polymer resin, or a mixture of two or more of them.

In the electrolyte according to the present disclosure, the lithium saltis an ionizable lithium salt and may be represented by Li⁺X⁻. The anion(X⁻) of the lithium salt is not particularly limited, but may compriseF⁻, Cl⁻, BR⁻, I⁻, NO₃ ⁻, N(CN)₂ ⁻, BF₄ ⁻, ClO₄ ⁻, PF₆ ⁻, (CF₃)₂PF₄ ⁻,(CF₃)₃PF₃ ⁻, (CF₃)₄PF₂ ⁻, (CF₃)₅PF⁻, (CF₃)₆P⁻, CF₃SO₃ ⁻, CF₃CF₂SO₃ ⁻,(CF₃SO₂)₂N⁻, (FSO₂)₂N⁻, CF₃CF₂(CF₃)₂CO⁻, (CF₃SO₂)₂CH⁻, (SF₅)₃C⁻,(CF₃SO₂)₃C⁻, CF₃(CF₂)₇SO₃ ⁻, CF₃CO₂ ⁻, CH₃CO₂ ⁻, SCN⁻, (CF₃CF₂SO₂)₂N⁻,or the like.

According to an embodiment of the present disclosure, the electrodeactive material layer may comprise 1-100 parts by weight of thepolymeric solid electrolyte based on 100 parts by weight of theelectrode active material. Within the above-defined range, the polymericsolid electrolyte may be used in an amount of 2 parts by weight or more,10 parts by weight or more, 20 parts by weight or more, 30 parts byweight or more, 50 parts by weight or more, or 70 parts by weight ormore, and 95 parts by weight or less, 90 parts by weight or less, 80parts by weight or less, 70 parts by weight or less, 60 parts by weightor less, 50 parts by weight or less, 40 parts by weight or less, or 30parts by weight or less. When the polymeric solid electrolyte is used inan amount larger than the upper limit, the proportion of the activematerial in the electrode is low to cause degradation of energy density.On the other hand, when the polymeric solid electrolyte is used in anamount smaller than the lower limit, the ion conductivity in theelectrode is reduced to cause a decrease in capacity realization.

According to the present disclosure, the conductive material is notparticularly limited, as long as it causes no chemical change in thecorresponding battery and has conductivity. For example, the conductivematerial comprise any one selected from: graphite, such as naturalgraphite or artificial graphite; carbon black, such as carbon black,acetylene black, Ketjen black, channel black, furnace black, lamp blackor thermal black; conductive fibers, such as carbon fibers (e.g. vaporgrown carbon fibers (VGCF)) or metallic fibers; metal powder, such ascarbon fluoride, aluminum or nickel powder; conductive whisker, such aszinc oxide or potassium titanate; conductive metal oxide, such astitanium oxide; and conductive materials, such as polyphenylenederivatives, or a mixture of two or more of them.

According to an embodiment of the present disclosure, the electrodeactive material layer may comprise the conductive material in an amountof 0-30 wt % based on 100 wt % of the electrode active material layer.According to an embodiment, the conductive material may be used in anamount of 0.5 wt % or more, 1 wt % or more, 3 wt % or more, or 5 wt % ormore, and 15 wt % or less, 10 wt % or less, 7 wt % or less, or 5 wt % orless, within the above-defined range. For example, the conductivematerial may be used in an amount of 0.5-5 wt % based on 100 wt % of theelectrode active material layer. When the amount of conductive materialis larger than the upper limit, the proportion of active material isreduced to cause a decrease in energy density. When the amount ofconductive material is smaller than the lower limit, it is not possibleto realize a desired level of electron conductivity, resulting indegradation of capacity realization.

According to an embodiment of the present disclosure, the electrode maybe any one of a negative electrode and a positive electrode. When theelectrode is a negative electrode, the negative electrode activematerial may be any material used conventionally as a negative electrodeactive material for a lithium ion secondary battery. For example, thenegative electrode active material may comprise at least one selectedfrom: carbon such as non-graphitizable carbon, graphitic carbon, or thelike; metal composite oxides such as Li_(x)Fe₂O₃ (0≤x 1), Li_(x)WO₂(0≤x≤1), Sn_(x)Me_(1−x)Me′_(y)O_(z) (Me: Mn, Fe, Pb or Ge; Me′: Al, B,P, Si, an element of Group 1, Group 2 or Group 3 in the Periodic Table,or halogen; 0<x≤1; 1≤y≤3; 1≤z≤8); lithium metal; lithium alloys;silicon-based alloys; tin-based alloys; metal oxides such as SnO, SnO₂,PbO, PbO₃, Pb₃O₃, Pb₃O₄, Sb₂O₃, Sb₂O₄, Sb₂O₅, GeO, GeO₂, Bi₂O₃, Bi₂O₄,Bi₂O₅, or the like; conductive polymers such as polyacetylene; Li—Co—Nibased materials; titanium oxide; and lithium titanium oxide, or thelike. According to an embodiment of the present disclosure, the negativeelectrode active material may comprise a carbonaceous material and/orSi.

When the electrode is a positive electrode, the positive electrodeactive material may be any material used conventionally as a positiveelectrode active material for a lithium ion secondary battery.Non-limiting examples of the positive electrode active material maycomprise, but are not limited to: layered compounds such as lithiumcobalt oxide (LiCoO₂) and lithium nickel oxide (LiNiO₂), or thosecompounds substituted with one or more transition metals(Li_(1+a)[Ni_(x)Mn_(y)Co_((1−x−y))]M_(z)O₂, wherein 0≤a≤0.2, 0.4≤x≤0.9,0<x+y<1, M is at least one element selected from the group consisting ofCo, Mn, Ni, Al, Fe, V, Cr, Ti, Ta, Mg, Mo, Zr, W, Sn, Hf, Nd and Gd, and0≤z≤0.1); lithium manganese oxides such as those represented by thechemical formula of Li_(1+x)Mn_(2−x)O₄ (wherein x is 0-0.33), LiMnO₃,LiMn₂O₃ and LiMnO₂; lithium copper oxide (Li₂CuO₂); vanadium oxides suchas LiV₃O₈, LiV₃O₄, V₂O₅ or Cu₂V₂O₇; Ni-site type lithium nickel oxidesrepresented by the chemical formula of LiNi_(1−x)M_(x)O₂ (wherein M isCo, Mn, Al, Cu, Fe, Mg, B or Ga, and x is 0.0100.3); lithium manganesecomposite oxides represented by the chemical formula ofLiMn_(2−x)M_(x)O₂ (wherein M=Co, Ni, Fe, Cr, Zn or Ta, and x=0.01-0.1)or Li₂Mn₃MO₈ (wherein M=Fe, Co, Ni, Cu or Zn); lithium manganesecomposite oxides having a spinel structure and represented by theformula of LiNi_(x)Mn_(2−x)O₄; LiMn₂O₄ in which Li is partiallysubstituted with an alkaline earth metal ion; disulfide compounds;Fe₂(MoO₄)₃; or the like.

According to an embodiment of the present disclosure, the positiveelectrode active material and/or negative electrode active material mayhave a particle diameter of about 0.01-50 μm, and may have a shape ofsecondary particles formed by aggregation of a plurality of particles.

The electrode active material layer may be formed on at least onesurface of a current collector. In addition, the electrode may furthercomprise a binder resin, if necessary.

According to the present disclosure, the binder resin is notparticularly limited, as long as it is an ingredient which assistsbinding between the electrode active material and the conductivematerial and binding to the current collector. Particular examples ofthe binder resin comprise polyvinylidene fluoride, polyvinyl alcohol,carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose,regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene,polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM),sulfonated EPDM, styrene butyrene rubber, fluororubber, variouscopolymers, or the like. In general, the binder resin is added in anamount of 1-30 wt %, or 1-10 wt %, based on 100 wt % of electrode activematerial layer.

According to an embodiment of the present disclosure, the electrode mayfurther comprise various additives in order to supplement or improve thephysicochemical properties thereof. Although there is no particularlimitation, the additives may comprise at least one of a flameretardant, heat stabilizer, anti-fogging agent, or the like.

According to the present disclosure, the current collector comprises ametal plate having electrical conductivity and may be one selectedsuitably depending on polarity of electrodes known in the field ofsecondary batteries. In addition, the current collector may have athickness controlled adequately within a range of 1-50 μm.

According to an embodiment of the present disclosure, the finishedelectrode (electrode active material layer) may have a porosity selectedadequately within a range of 0-18%. According to an embodiment of thepresent disclosure, the porosity may be 1% or more, 3% or more, 5% ormore, 7% or more, 10% or more, or 15% or more, or 17% or more, and 18%or less, 15% or less, 10% or less, 7% or less, or 5% or less. Forexample, the porosity may be 1-15% or 5-18%.

Since an all solid-state battery uses an electrolyte in a solid phaserather than a liquid phase, the contact area between the electrodeactive material and the solid electrolyte material is increased and theelectrode active material is in closer contact with the solidelectrolyte material, as the porosity is decreased, thereby realizing adesired level of ion conductivity. According to an embodiment of thepresent disclosure, the electrode for an all solid-state batterypreferably has low porosity sufficient to realize a desired level of ionconductivity.

The term ‘porosity’ means a ratio of volume occupied by pores based onthe total volume of a given structure, is expressed in the unit of %,and may be used interchangeably with the term of pore ratio or porousdegree. According to the present disclosure, the porosity may bedetermined by any method with no particular limitation. For example, theporosity may be determined by using the Brunauer-Emmett-Teller (BET)method or Hg intrusion porosimetry. According to an embodiment of thepresent disclosure, the apparent density of a finished electrode(electrode active material layer) is calculated from the volume andweight of a finished electrode (electrode active material layer) and thenet density of an electrode active material layer is calculated from thecompositional ratio of ingredients contained in the electrode (electrodeactive material layer) and density of each ingredient. Then, theporosity of an electrode active material layer may be calculated fromthe difference between the apparent density and the net density.

Hereinafter, the method for manufacturing the above-described electrodewill be explained. The following method is one of the embodiments thatmay be applied to manufacture the electrode according to the presentdisclosure and the scope of the present disclosure is not limitedthereto.

First, slurry for forming an electrode active material layer containingelectrode active material particles, a polymeric solid electrolyte and aconductive material is prepared (S1).

Particularly, a mixture containing a polymeric solid electrolyte and aconductive material is prepared. The polymeric solid electrolyte may beprovided in the form of a melt blend obtained by melting a polymer resinand lithium salt at high temperature or in the form of a solutioncontaining a polymer resin and lithium salt dispersed homogeneously inan organic solvent. Then, the conductive material is added to the blendor solution, followed by mixing, to provide a mixture. The mixture mayfurther comprise a binder resin, if necessary. In addition, electrodeactive material particles are added thereto and mixed to prepare slurryfor forming an electrode active material layer. The content of each ofthe electrode active material and polymeric solid electrolyte in theslurry may be the same as described above.

However, the above-mentioned method for preparing slurry is an exemplaryembodiment and the scope of the present disclosure is not limitedthereto. Particularly, the order of introduction or mixing of slurryingredients may be modified considering the physicochemical propertiesof ingredients and the characteristics of an electrode or battery to beobtained. For example, the polymeric solid electrolyte, conductivematerial and the electrode active material may be introduced to adispersion medium, such as a solvent, at different times or at the sametime.

Next, the slurry is coated on at least one of a current collector toobtain a preliminary electrode (S2). As used herein, ‘preliminaryelectrode’ means an electrode not subjected to solvent annealing.

The coating may be carried out by applying the slurry onto at least onesurface of a current collector, followed by drying, and performingcompression, if necessary. The slurry may be applied by using aconventional slurry coating process, such as doctor blade coating orslot die coating. Then, the applied slurry is dried and subjected to acompression process, if necessary. The compression process allowspacking of ingredients so that the electrode active material layer mayhave an adequate level of porosity and is not limited to a particularmethod. For example, any known compression method, such as hot pressingor rolling, may be used suitably, and may be optionally controlled to asuitable temperature condition through heating or cooling.

After that, the resultant preliminary electrode is subjected to asolvent annealing process (S3). During the solvent annealing, thepolymeric solid electrolyte is exposed to a vaporized organic solventand the vaporized organic solvent infiltrates into the solid electrolyteto cause volumetric swelling of the electrolyte. The solvent annealingprocess may comprise the steps of: introducing the preliminary electrodeto a sealed space (e.g. chamber); filling the sealed space with avaporized solvent; and allowing the preliminary electrode to stand inthe sealed space filled with the vaporized solvent.

In the step of allowing the preliminary electrode to stand in the sealedspace, the vaporized solvent infiltrates into the polymeric solidelectrolyte, and thus the polymeric solid electrolyte is swelled.According to an embodiment of the present disclosure, the sealed spacemay be filled with the vaporized solvent by vaporizing the solvent in aseparate space linked to the chamber through a pipe and injecting thevaporized solvent to the chamber. In a variant, a liquid solvent isreceived in a separately prepared container, the container is introducedto a chamber, and the chamber is heated so that the solvent may bevaporized directly in the chamber. Herein, it is preferred that theliquid solvent is spaced apart from the electrode by a predeterminedinterval so that they may not be in direct contact with each other.

Meanwhile, it is possible to change the order of the step of introducingthe preliminary electrode to a sealed space (e.g. chamber) and the stepof filling the sealed space with the vaporized solvent, if necessary.For example, the chamber may be filled with the vaporized solvent beforethe preliminary electrode is introduced to the chamber. According to anembodiment of the present disclosure, the vaporization step may becarried out at a temperature ranging from about 15-200° C., consideringthe vapor pressure or boiling point of the solvent. For example, thevaporization step may be carried out at room temperature of about 20-30°C. or may be carried out at a higher temperature, such as about 200° C.or lower, through heating. In other words, according to an embodiment ofthe present disclosure, the vaporized solvent may have a temperature ofabout 15-200° C., and solvent annealing may be carried out in thechamber filled with the vaporized solvent at the above-defined range oftemperature for a predetermined time. Unless otherwise stated herein,temperature is described in a Celsius temperature scale.

According to an embodiment of the present disclosure, the sealed space,such as a chamber, in which solvent annealing is carried out should besaturated with the vaporized solvent. To accomplish this, the sealedspace is maintained at least under the vapor pressure of the solvent.According to an embodiment of the present disclosure, the vaporizedsolvent may be introduced continuously until the solvent annealing isterminated. Otherwise, when the liquid solvent is also introduced to thechamber and heated, an excessive amount of solvent is introduced so thatthe solvent may not be totally vaporized but a residual amount ofsolvent may remain until the solvent annealing process is terminated.The amount of solvent may be determined considering the amount (volumeor weight) of the polymeric solid electrolyte used for the electrodeand/or chamber size. For example, when using N-methyl pyrrolidone (NMP)is used as a solvent, the chamber may have a size of about 300 mL, andsolvent annealing is carried out at 130° C. for 24 hours, about 300 μLof NMP may be introduced.

According to an embodiment of the present disclosure, the solvent usedfor solvent annealing is not particularly limited, as long as it ischemically stable and particularly it causes no deterioration of anelectrode when being applied to the electrode. For example, it ispossible to use a solvent selected from solvents that may be used aselectrolytes for electrochemical devices. For example, the solvent maycomprise at least one selected from cyclic, linear or branchedcarbonates, linear esters, ethers, or the like. Non-limiting examples ofsuch solvents may comprise propylene carbonate (PC), ethylene carbonate(EC), butylene carbonate (BC), diethyl carbonate (DEC), dimethylcarbonate (DMC), dipropyl carbonate(DPC), methyl propionate (MP),dimethyl sulfoxide, dimethoxyethane, diethoxyethane, tetrahydrofuran,N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), vinylenecarbonate (VC), gamma-butyrolactone (GBL), fluoroethylene carbonate(FEC), methyl formate, ethyl formate, propyl formate, methyl acetate,ethyl acetate, propyl acetate, pentyl acetate, methyl propionate, ethylpropionate, propyl propionate, butyl propionate, or the like.

In addition, the solvent may comprise at least one of an aprotic solventselected from N,N-dimethyl acetamide (DMAc), N-methyl pyrrolidone (NMP),dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), tetrahydrofuran(THF), acetonitrile, benzene, butyl acetate, chloroform, cyclohexane,1,2-dichloroethane, ethyl acetate, diethyl ether, hexane, heptane,pentane, xylene or toluene; or a protic solvent selected from water,methanol, ethanol, propanol, n-butanol, isopropyl alcohol, decalin,acetic acid or glycerol.

In addition, solvent annealing may be carried out for 1-72 hours and thesolvent annealing time may be controlled adequately. For example, thesolvent annealing time may be 2 hours or more, 10 hours or more, 20hours or more, 30 hours or more, or 50 hours or more, or 65 hours orless, 60 hours or less, 50 hours or less, 40 hours or less, or 30 hoursor less, within the above-defined range. When the annealing time iswithin the above-defined ranges, solvent annealing may be carried outefficiently through solvent evaporation. In addition, when the annealingtime is longer than the above-defined range, productivity is decreaseddue to an increase in electrode processing time. When the annealing timeis shorter than the above-defined range, the polymeric solid electrolyteforming the electrolyte may not be swelled homogeneously.

Meanwhile, according to an embodiment of the present disclosure, acompression step may be further carried out in order to control theporosity, after completing the solvent annealing.

In the electrode obtained from the above-described method, the polymericsolid electrolyte is swelled by solvent infiltration and is packed inthe electrode active material layer. Thus, the active material particlesare closely bound with the polymeric solid electrolyte and theconductive material through face-to-face and dot-to-dot binding, therebyproviding an integrated electrode structure.

The electrode obtained from the above-described method may be suppliedto a process for manufacturing an electrode assembly for an allsolid-state battery and/or an all solid-state battery. Herein, it ispreferred that the solid electrolyte is introduced to the subsequentprocess, while maintaining its swelled state after the annealing.

FIG. 1 is a schematic view illustrating the electrode obtained by theconventional method for manufacturing an electrode. According to theconventional method, the electrode 100 is obtained by mixing electrodeactive material particles 121, a polymeric solid electrolyte 122 and aconductive material 123 all at once to prepare electrode slurry, andcoating the slurry onto a current collector. In this case, the electrodeactive material is not in close contact with the solid electrolyte andthe contact area is small, and thus it is not possible to ensuresufficient electrochemical reaction sites between the electrode activematerial and the solid electrolyte. As a result, there are problems inthat battery performance cannot be realized sufficiently due to adecrease in capacity, degradation of output characteristics, a decreasein ion conductivity, an increase in interfacial resistance, or the like.To solve the above-mentioned problems, there is a need for a compressionstep in which the electrode surface is compressed under a high pressurecondition after coating the electrode in order to increase the contactarea between the electrode active material and polymeric solidelectrolyte. However, in this case, there are problems in that theactive material is cracked due to the high pressure applied during thecompression step, resulting in degradation of battery capacity and lifecharacteristics.

FIGS. 2 and 3 are schematic views illustrating the electrode 200, 300according to an embodiment of the present disclosure. Referring to FIGS.2 and 3, the electrode active material layer 220, 320 is formed on onesurface of the current collector 210, 310, and the polymeric solidelectrolyte 222, 322 in the electrode active material layer 220, 320 isswelled homogeneously as a whole by the solvent steam (shown by thearrow mark in FIG. 2) infiltrating during the solvent annealing processso that the electrode active material particles 221, 321 and the solidelectrolyte 222, 322 may be in close contact with each other and thearea of electrochemical reaction sites may be increased. In addition,the conductive material 223, 323 is positioned near the surface of theelectrode active material particles 221, 321, and thus participates inelectrochemical reactions at a higher ratio. As a result, use ofconductive material can be reduced. In addition, the solid electrolyteand the electrode active material are in good contact with each othereven when no severe pressure is applied during the compression of theelectrode. Thus, it is possible to ensure sufficient reaction sites andto prevent deterioration of the electrode caused by compression.Further, it is possible to increase lithium ion transportability andcapacity realization of the active material.

In another aspect of the present disclosure, there is provided a lithiumion secondary battery comprising one or more of the above-describedelectrode. The battery comprises a positive electrode, a negativeelectrode and a solid electrolyte membrane interposed between thepositive electrode and the negative electrode, wherein at least one ofthe negative electrode or the positive electrode is the above-describedelectrode according to the present disclosure.

According to the present disclosure, the solid electrolyte membrane isinterposed between the negative electrode and the positive electrode,and functions to allow lithium ion to pass therethrough whileelectrically insulating the negative electrode and the positiveelectrode from each other. The solid electrolyte membrane may be anysolid electrolyte membrane used conventionally in the field of allsolid-state batteries with no particular limitation. According to anembodiment of the present disclosure, the solid electrolyte membrane isprepared in the shape of a film or membrane, and may be a free-standingtype membrane interposed between the electrodes or may be coated on theelectrodes in the form of a membrane or film.

According to an embodiment of the present disclosure, the solidelectrolyte membrane may comprise at least one of the solid electrolyteingredients used for the electrode according to the present disclosure.In addition, the solid electrolyte membrane may comprise an inorganicsolid electrolyte ingredient independently from or in combination withthe above-described polymeric solid electrolyte ingredients. Theinorganic solid electrolyte may be at least one selected fromsulfide-based solid electrolytes or oxide-based solid electrolytes, andany inorganic solid electrolyte may be used with no particularlimitation, as long as it is used generally as a solid electrolyte foran all solid-state battery.

In still another aspect of the present disclosure, there are provided abattery module comprising the secondary battery as a unit cell, abattery pack comprising the battery module, and a device comprising thebattery pack as a power source.

Herein, particular examples of the device may comprise, but are notlimited to: power tools driven by an electric motor; electric cars,comprising electric vehicles (EV), hybrid electric vehicles (HEV),plug-in hybrid electric vehicles (PHEV), or the like; electric carts,comprising electric bikes (E-bikes) and electric scooters (E-scooters);electric golf carts; electric power storage systems; or the like.

Examples will be described more fully hereinafter so that the presentdisclosure can be understood with ease. However, the following examplesare for illustrative purposes only and the scope of the presentdisclosure is not limited thereto.

EXAMPLES Manufacture of Electrode and Battery Example 1

(1) Manufacture of Electrode

First, NCM811 (LiNi_(0.8)Co_(0.1)Mn_(0.1)O₂) as an electrode activematerial, vapor grown carbon fibers (VGCF) as a conductive material anda polymeric solid electrolyte (a mixture of polyethylene oxide (PEO)with LiFSI ((LiCF₃SO₂)₂N), molar ratio of PEO:LiFSI, [EO]:[Li⁺]=20:1)were mixed at a weight ratio of 80:3:17 and the resultant mixture wasintroduced to acetonitrile, followed by agitation, to provide electrodeslurry. An aluminum current collector having a thickness of 20 μm wasprepared. The slurry was applied to the current collector by using adoctor blade and the resultant product was vacuum-dried at 120° C. for 4hours. Then, compression was carried out by using a roll press device toobtain a preliminary electrode having a loading amount of 2 mAh/cm², anelectrode active material layer thickness of 48 μm and a porosity of22%.

Then, the electrode was introduced to a chamber (300 mL) and 300 μL ofN-methyl pyrrolidone (NMP) was introduced to the chamber together withthe electrode in such a manner that the solvent might not be in directcontact with the electrode. The chamber was sealed and was maintained at60° C. for 24 hours to carry out solvent annealing. In this manner, anelectrode comprising an electrode active material layer having aporosity of 10% was obtained. The porosity means the ratio of volume ofpores (pore volume) occupied by pores based on the total volume. Theporosity was calculated by using the apparent density calculated fromthe volume and weight of each electrode active material layer and thenet density calculated from the compositional ratio of the ingredientsand density of each ingredient, as well as the pore volume obtainedtherefrom.

(2) Manufacture of Battery

The electrode obtained from (1) was cut into a circular shape with anarea of 1.4875 cm². Lithium metal foil cut into a circular shape with anarea of 1.7671 cm² was prepared as a counter electrode. Then, a solidelectrolyte membrane (a mixture of PEO with LiFSI ((LiCF₃SO₂)₂N), molarratio of PEO:LiFSI, [EO]:[Li⁺]=20:1) having a thickness of 50 μm wasinterposed between both electrodes to obtain a coin type half-cell.

Example 2

An electrode and a battery were manufactured in the same manner asExample 1, except that solvent annealing was carried out at roomtemperature. Before solvent annealing, the electrode active materiallayer had a porosity of 22%. After solvent annealing, the electrodeactive material layer had a porosity of 16%.

Example 3

An electrode and a battery were obtained in the same manner as Example1, except that solvent annealing was carried out at 100° C. for 6 hours.Before solvent annealing, the electrode active material layer had aporosity of 22%. After solvent annealing, the electrode active materiallayer had a porosity of 12%.

Comparative Example 1

An electrode and a battery were obtained in the same manner as Example1, except that solvent annealing was not carried out. The electrodeactive material layer had a porosity of 22%.

Test Example 1 Evaluation of Initial Discharge Capacity and OutputCharacteristics

Each of the batteries according to Examples 1-3 and Comparative Example1 was charged/discharged to evaluate the initial discharge capacity andcapacity retention. Meanwhile, when evaluating output characteristics,the first charge/discharge were carried out at 60° C. and 0.05 C, the30^(th) cycle was terminated in a discharged state, and capacityretention was evaluated.

Charge condition: CC (constant current)/CV (constant voltage), (4.0V or4.25V, 0.005 C current cut-off)

Discharge condition: CC (constant current), 3V

The capacity retention was derived by calculating the ratio of dischargecapacity after 30 cycles based on discharge capacity at the first cycle.The results are shown in the following Table 1.

TABLE 1 Discharge capacity Output characteristics (%) (mAh/g, 4.0 V) 0.2C/0.05 C, 4.0 V Example 1 136 70 Example 2 131 67 Example 3 135 68 Comp.Ex. 1 126 61

As can be seen from the above results, in the case of Examples 1-3, thepolymer electrolyte in the electrode active material layer is swelled bythe solvent annealing process to cause an increase in contact areabetween the electrode active material layer and the solid electrolyte,thereby accelerating intercalation/deintercalation of ions to/from theactive material. As a result, the capacity and output characteristicsare improved as compared to Comparative Example 1.

1. An electrode for an all solid-state battery which comprises anelectrode active material layer comprising a plurality of electrodeactive material particles, a polymeric solid electrolyte and aconductive material, wherein the gaps between the electrode activematerial particles are filled with the polymeric solid electrolyte, thepolymeric solid electrolyte comprises a swellable polymer electrolyte,the polymeric solid electrolyte is in a swelled state by solventinfiltration, and the electrode active material layer has a porosity of0-18%.
 2. The electrode for an all solid-state battery according toclaim 1, wherein the polymeric solid electrolyte in the swelled state isobtained through volumetric swelling by the solvent infiltration of avaporized organic solvent.
 3. The electrode for an all solid-statebattery according to claim 1, wherein the polymeric solid electrolyte inthe swelled state is obtained through a solvent annealing process,wherein the porosity of the electrode active material layer is reducedby the solvent annealing process and the difference in porosity betweenbefore and after the solvent annealing process is 0.5% or more.
 4. Theelectrode for an all solid-state battery according to claim 3, whereinthe porosity of the electrode active material layer is reduced byswelling of the polymeric solid electrolyte after the solvent annealingprocess.
 5. The electrode for an all solid-state battery according toclaim 1, wherein the polymeric solid electrolyte is a solid polymerelectrolyte formed by adding a polymer resin to a solvated lithium salt.6. An all solid-state battery comprising a positive electrode, anegative electrode and a solid electrolyte layer interposed between thepositive electrode and the negative electrode, wherein at least one ofthe positive electrode and the negative electrode is the electrode asdefined in claim
 1. 7. A method for manufacturing an electrode for anall solid-state battery, comprising the steps of: preparing a slurry forforming an electrode active material layer containing electrode activematerial particles, a polymeric solid electrolyte and a conductivematerial; coating the slurry on at least one surface of a currentcollector to obtain a preliminary electrode; and subjecting thepreliminary electrode to a solvent annealing process to obtain anelectrode.
 8. The method for manufacturing an electrode for an allsolid-state battery according to claim 7, wherein the polymeric solidelectrolyte is a solid polymer electrolyte formed by adding a polymerresin to a solvated lithium salt.
 9. The method for manufacturing anelectrode for an all solid-state battery according to claim 7, whereinthe solvent annealing process comprises the steps of: introducing thepreliminary electrode to a sealed space; filling the sealed space with avaporized solvent; and allowing the preliminary electrode to stand inthe sealed space filled with the vaporized solvent.
 10. . The method formanufacturing an electrode for an all solid-state battery according toclaim 7, wherein the solvent annealing process is carried out for 1-72hours.
 11. The method for manufacturing an electrode for an allsolid-state battery according to claim 9, wherein the solvent is atleast one of an aprotic solvent selected from N,N-dimethylacetamide(DMAc), N-methyl pyrrolidone (NMP), dimethyl sulfoxide (DMSO) orN,N-dimethylformamide (DMF); or a protic solvent selected from water,methanol, ethanol, propanol, n-butanol, isopropyl alcohol, decalin,acetic acid or glycerol.
 12. The method for manufacturing an electrodefor an all solid-state battery according to claim 7, wherein thepolymeric solid electrolyte undergoes volumetric swelling by theinfiltration of a vaporized organic solvent in the solvent annealingprocess.
 13. The method for manufacturing an electrode for an allsolid-state battery according to claim 7, wherein the solvent annealingprocess is carried out at a temperature of 15-200° C.
 14. The electrodefor an all solid-state battery according to claim 1, wherein theswellable polymer electrolyte is included in an amount of 50 vol % ormore in the polymeric solid electrolyte.
 15. The electrode for an allsolid-state battery according to claim 1, wherein the polymer solidelectrolyte comprises a polycarbonate-based polymer electrolyte, apolysiloxane-based polymer electrolyte, a phosphazene-based polymerelectrolyte, or a polyether-based polymer electrolyte.
 16. The electrodefor an all solid-state battery according to claim 1, wherein the polymersolid electrolyte comprises one selected from the group consisting of apolyether polymer, polycarbonate polymer, acrylate polymer, polysiloxanepolymer, phosphazene polymer, polyethylene derivatives, alkylene oxidederivatives, phosphate polymer, polyagitation lysine, polyester sulfide,polyvinyl alcohol, polyvinylidene fluoride and polymer containing anionically dissociable group, or a mixture thereof.
 17. The electrode foran all solid-state battery according to claim 1, wherein the electrodeactive material layer comprises 1-100 parts by weight of the polymericsolid electrolyte based on 100 parts by weight of the electrode activematerial particles.
 18. The electrode for an all solid-state batteryaccording to claim 1, wherein the electrode active material layercomprises the conductive material in an amount of 0-30 wt % based on 100wt % of the electrode active material layer.
 19. The method formanufacturing an electrode for an all solid-state battery according toclaim 7, wherein the polymeric solid electrolyte is swelled at aswelling degree of larger than 1% to 1,000% after the solvent annealingprocess.
 20. The method for manufacturing an electrode for an allsolid-state battery according to claim 7, further comprising compressingthe electrode after the solvent annealing process.